A Quantitative Study of the Pettenkofer Reaction for Bile Salts.

Abstract

As originally described this is a qualitative test for bile salts and is performed by dissolving a small amount of bile, or, the bile containing fluid, in concentrated H₂SO₄ and adding a few drops of a 10 per cent solution of cane sugar. In the presence of bile salts the solution assumes a red-purple color which approaches a violet within the course of a day. As shown by a number of investigators, the reaction may be satisfactorily carried out in a 50 per cent H₂SO₄ solution.

In attempting to use the Mylius modification of the Pettenkofer reaction quantitatively, which employs furfural instead of cane sugar, it was never possible to obtain color matches. It has been found that by performing the reaction in weaker concentrations of H₂SO₄ (30 to 40 per cent) a blue color is developed. This color is due to an absorption bond at 6200 A and seems suitable for quantitative colorimetric determinations. Color matches are easily obtained when the solution being tested contains twice as much bile salt as the standard. When the tested solution is within 50 per cent of the strength of the standard the error is never greater than 5 per cent. It is usually about 2 per cent. This error increases to 10 per cent when the tested solution differs from the standard by 100 per cent.

Glycocoll, taurine, cholesterol, a cholesterol ester (lanodin), lecithin, kephalin, and oleic acid do not give any color reaction in the weaker H₂SO₄, solution mentioned. Oleic acid and the phosphatides are known to give a red color when the reaction is carried out in higher concentrations of H₂SO₄. Isobutyl and amyl alcohol also give a red color reaction with furfural in SO per cent H₂SO₄.